During surgery to repair ligament and/or tendon damage, it is sometimes necessary to insert an interference or fixation screw into a bone. The screw provides a secure attachment for the repaired tissue or graft. However, screws may also damage the graft or the surrounding tissue during the insertion procedure. Protective devices, such as cannulated sheaths, are known which protect the surrounding tissue from undesired contact with the threads of the screw, thereby reducing collateral damage to the surgical site. The screw and a driver therefor are inserted into the hollow interior of the sheath. The screw is allowed to fall to the distal end of the sheath. The driver forces the screw out of the distal end of the sheath, however, the screw is free to move laterally and longitudinally within the distal end of the sheath. Other protective sheaths have a cut-out at the distal end exposing the threads of the screw to a graft tunnel in the surgical site and to surrounding tissue (see U.S. Pat. Nos. 5,211,647 and 5,425,733). This type of sheath may undesirably allow the threads of the screw extending through the cut-out to undesirably damage the graft or the surrounding tissue.
Accordingly, it is the object of the present invention to provide a screw sheath having a cannulated body which completely encloses the screw positioned therein until the screw exits the screw sheath and enters a tunnel in the surgical site, thereby preventing collateral damage to a graft or surrounding tissue by threads on the screw.
A further object of the invention is to provide a cannulated screw sheath, as aforesaid, with a protrusion extending into the hollow interior thereof, which protrusion engages the threads on the screw and secures the screw at a distal end of the screw sheath so as to prevent longitudinal movement of the screw therein absent rotary movement of the screw.
It is a further object of the invention to provide a screw sheath, as aforesaid, which is transparent to allow visual verification of the position of the screw within the screw sheath.
It is a further object of the invention to provide a screw sheath, as aforesaid, wherein the screw is secured at the distal end of the screw sheath without the threads thereof boring into the interior walls of the sheath to prevent the creation and deposit of shavings of the screw sheath material in the surgical site.